Underground bus duct

[bigfish92]

I have an underground bus duct run from a panel to a number of motors, panels, lights, etc. I am trying to combine as many circuits in the same duct as possible to reduce the number of ducts. I have 2 480v motors that I am running in the same duct ( 20% load adjustment) Can I install the control conductors (120V) for these motors in with other 120 V conductors in the same duct? Maximum wires is 7 in that duct.

 

[websparky]

Re: Underground bus duct

If I understand your question correctly;

NEC 2002 300.3 Conductors.(4)(C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of circuits rated 600 volts, nominal, or less, ac circuits, and dc circuits shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

Hope this helps.
Dave

 

[don_resqcapt19]

Re: Underground bus duct

In my opinion the control wiring is an Article 725 Class 1 circuit. Look at 725.26(B)(1). These control conductors can only be installed in the same racway as power conductors if the condtrol conductors are functionally associated with the power conductors.
Don

 

[websparky]

Re: Underground bus duct

Hi Don,

You bring up a very good point!
It made me dig a little deeper.

NEC 2002
725.3 Locations and Other Articles.
Circuits and equipment shall comply with the articles or sections listed in 725.3(A) through (F). Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.

After reading this, I think we are in the clear with 300.3?

Thanks,
Dave

 

[pierre]

Re: Underground bus duct

Try this

Remember that Chapters 5, 6, 7 & 8 modify or amend Chapters 1 thru 4. In Article 725 it has to SPECIFICALLY mention an Article/Section in Chapter 3.

725.3 Locations and Other Articles.
Only those sections of article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits. 2002 NEC (reference)

300.3 is not referenced, therefore it is not to be used in this application.

725.26(A) & 725.26(B)(1) should be referenced.

The 120v conductors can all be in the same enclosure/raceway if the are all Class 1 conductors, and do not include power conductors of any kind. 725.26(A)

If you want to install the feeders for the motor and it's control circuit in the same raceway or enclosure, you can (725.26(B)(1)).

Hope this is helpful

Pierre